Discount codes are provided to members of a few organizations that have agreements with the various fitness agencies. If you are a member of IDEA, for example, there are discounts offered between them and ACE. You need to check with any groups that you are affiliated with for this type of thing.
I do believe that even if you were to get a code somehow and attempted to use it, the computer program for the codes would verify whether or not you were entitled to the discount. (ie. the system cross checks whether your name is on a list of eligible users.)